4. Electronic Theses and Dissertations (ETDs) - Faculties submissions
Permanent URI for this communityhttps://hdl.handle.net/10539/37773
Browse
667 results
Search Results
Item Synthesis and characterization of onion-like carbons for adsorption of tartrazine dye in water(University of the Witwatersrand, Johannesburg, 2024-08) Cwayi, Herbert Qaqambile; Maubane-Nkadimeng, Manoko S.; Coville, Neil J.; Maboya, Winny K.Industrial effluent often can contain a significant amount of synthetic dyes. The discharge of wastewater containing dyes into water streams without proper treatment consequently enters the soil and disturbs the aquatic and terrestrial life. Several wastewater treatment technologies have been proposed that can efficiently reduce the amount of synthetic dyes from the environment, in particular azo dyes. Among all the existing technologies for wastewater treatment, physical adsorption is a popular technology because it is inexpensive, simple, and efficient. The aim of this study is to synthesize, modify, and characterize onion-like carbons (OLCs) derived from four different waste oils for the adsorption of tartrazine dye in water. The OLCs derived from different carbon precursors (waste household oil, restaurant waste oil, engine waste oil, and paraffin oil bath waste) were synthesized using a flame pyrolysis method. The synthesized materials were doped with nitrogen using a chemical vapor deposition technique using 10% ammonia gas as a source of nitrogen. The N-doped OLCs were attached with hydroxyl groups through oxidation reactions to improve their solubility and adsorption efficacy. According to the high-resolution transmission electron microscopy and scanning electron microscopy images, the OLCs from all four-carbon precursor were quasi-spherical, agglomerated, and presented a chain-like structures of multi-layers. The distance between the graphitic layers was found to be 0.32 nm. The average particle size of OLCs was calculated to be 40.2 ± 2.5 nm. Adsorption studies revealed that the initial dye concentration, contact time, and pH of the dye solutions influenced the adsorption capacity of the tetrazine. Nitrogen doping of OLCs increased its capacity to adsorb the tartrazine dye. The nitrogen doped OLCs from household waste oil (H-N-OLCs) and engine waste oil (E-N- OLCs) were used in equilibrium adsorption studies in this work. For a concentration of 20 mg/L of tartrazine dye, an adsorption capacity of 28.9 mg/g was achieved using the N- doped OLCs from household waste oil. The adsorption process follows the pseudo second- order kinetic model. The adsorption isotherm is best fitted to the Freundlich mathematical model. The results obtained show that, the source of oil did not have major effect on the physicochemical properties of OLCs and that incorporation of nitrogen onto carbon matrix enhanced the adsorption of the anionic tartrazine dye in aqueous solution.Item Unveiling the biochemical pathway between Type 2 Diabetes Mellitus and early Alzheimer’s disease(University of the Witwatersrand, Johannesburg, 2024-08) Tooray, Shweta; van der Merwe, EloiseResearch related to Alzheimer's Disease (AD) remains a focal point in neurodegeneration studies. This is due to the severity of AD and the clear necessity for non-palliative treatment approaches, as underscored by the high prevalence of the disease. The combined formation of extracellular senile plaques and neurofibrillary tangles (NFTs) plays a crucial role in the development of the cognitive and behavioural symptoms observed in individuals with AD. Despite extensive research efforts, discovering a definitive cure for the disease remains a challenge. Therefore, it is imperative to explore new perspectives and identify the upstream molecular mechanisms that contribute to the onset of the disease. Metabolic disorders are widely recognized as a significant risk factor for AD. Specifically, the metabolic syndrome, Type 2 Diabetes Mellitus (T2DM), is connected to neurodegeneration by promoting the accumulation of neurotoxins, inducing neuronal stress, affecting synaptic communication, and leading to brain atrophy. Individuals with T2DM have an increased risk of developing dementia, with hyperglycaemia exacerbating the impact of AD by causing mitochondrial dysfunction and oxidative stress through reactive oxygen species (ROS) formation, which are also present in AD. Additionally, patients with T2DM exhibit shorter telomeres linked to cell death, which is an associated risk factor for developing AD. These key pathways involved in connecting T2DM and AD were explored in the current study to enhance the understanding of the early events that precede AD. Glucose uptake was measured and observed to decrease over time as a potentially protective response of the cell. Subsequently, mitochondrial activity, assessed using the Alamar blue assay, was found to be heightened as an initial protective mechanism of Aβ42. This was later overwhelmed by the elevated ROS detected through a Total ROS assay kit, induced by the hyperglycaemic state of T2DM. In turn causing the amount of Aβ42 to become toxic and leading to a decline in mitochondrial DNA (mtDNA) over time as measured through qPCR. Additionally, the increases in ROS induced by hyperglycaemia resulted in oxidative damage to telomeres. Simultaneously, Aβ42 physically hinders telomere-telomerase binding, leading to reduced telomerase activity and consequently, shorter telomeres. Furthermore, this study reveals, for the first time, that the novel glucose-lowering drug (GLD) caused an increase in Aβ42 production in the T2DM cell model, whilst effectively decreasing ROS production over a 24-hour period compared to the untreated cell model. The rise in Aβ42 levels caused by GLD could potentially be working to prevent the increase in hyperglycaemia-induced ROS through its metal chelating antioxidant properties by scavenging ROS, in the presence of oxidative stress associated with T2DM. These findings are indicative of an appealing function of GLD by reducing ROS and thereby impeding the progression towards AD. Hence making GLD an attractive therapeutic option for the treatment and/or prevention of AD.Item Growth effects of human capital and innovation in small and medium sized South African firms before and after the Covid-19 pandemic(University of the Witwatersrand, Johannesburg, 2024) Maingehama, Francisca Nyasha; Callaghan, ChrisThis thesis examines the growth of small and medium-sized enterprises (SMEs) in South Africa before and after the COVID-19 pandemic. The COVID-19 pandemic introduced new challenges, which makes this research relevant for contemporary issues in firm growth. The problem addressed in this study was the need to understand how various factors, such as human capital, innovation, entrepreneurial orientation and motivation, affect SME growth. Previous research has focused mainly on organisational-level determinants without considering how these factors interact in a post-COVID-19 context. This gap is particularly relevant in South Africa, where SMEs face high failure rates despite efforts to support entrepreneurship. The study filled this gap by exploring the specific growth dynamics of SMEs in this contemporary and challenging context. Several key research questions guided the study and aimed to achieve two main objectives. The study used a two-phase methodology. First (Phase 1), it systematically reviewed the literature to synthesise knowledge on human capital, innovation, and firm growth before the COVID-19 pandemic. The systematic literature review analysed 206 articles published between 2000 and 2020 using descriptive statistics, bibliometric analysis, and content analysis to synthesise pre-pandemic research. Secondly (Phase 2), it developed and tested a theoretical model to understand the relationship between human capital, innovation, entrepreneurial orientation, motivation and SME growth in South Africa post- pandemic. In this phase, primary data was collected using a structured questionnaire with 497 responses from small firm owner-managers and analysed using Smart PLS (version 3.2.9). This research adopted a positivist philosophy, focussing on empirical patterns and causal relationships. Key findings indicated that innovation mediates the relationships between entrepreneurial orientation, human capital, and the growth of SMEs. Human capital has a direct impact on firm growth in the post-pandemic context. At the same time, motivation significantly mediated the link between entrepreneurial orientation and growth, though its effect on the human capital-growth relationship was less pronounced. This study advances knowledge by providing a detailed analysis of SME growth determinants in a post-pandemic context, offering a customised theoretical model for South African SMEs. This study also has practical implications, providing insight for SMEs and policymakers to enhance innovation capabilities and adapt strategies to post-pandemic challenges. Future research could explore the long-term ii impacts of COVID-19 on firm growth, the role of additional contextual variables, and comparative studies in different regions or sectors.Item Comparison of different bioassay methods for the assessment of dose-response relationships of entomopathogens and toxins against Helicoverpa armigera (Hübner, 1809) (Lepidoptera: Noctuidae)(University of the Witwatersrand, Johannesburg, 2024-11) Mogadingoane, Keitumetse Neo; Bouwer, GustavBioassays are an important tool for developing bioinsecticides against agricultural pests. The aim of this study was to compare two bioassay methods – diet overlay and droplet feeding – to identify the most suitable method for assessing dose-response relationships of entomopathogens and toxins against second instar larvae of Helicoverpa armigera. The toxins used were purified Bacillus thuringiensis Cry1A.105 and Cry2Ab2.820 proteins, the spore-crystal complex (SCC) of B. thuringiensis subspecies kurstaki strain HD-73, and the entomopathogen Helicoverpa armigera nucleopolyhedrovirus (HearNPV). Based on the heterogeneity factor, coefficient of variance (CV) and relative precision, the diet overlay bioassay was determined to be the best fit for use with HD-73 SCC and HearNPV. Suitable bioassay methods could not be determined for the purified B. thuringiensis proteins due to a poor probit model fit and low precision of estimated LC50s and LD50s. Validation of CV and relative precision across bioassays will ensure the most suitable methods are used for sustainable integrated pest management.Item The effect of parental education on child and adult health in Zambia: A regression discontinuity analysis(University of the Witwatersrand, Johannesburg, 2024) Daka, Lincoln; Booysen, FrederikThis thesis expands upon and enhances existing research in the field of health economics. The thesis consists of three separate yet interrelated chapters that examine the effect of education on key demographic variables: child health, fertility and HIV/AIDS in Zambia, three key factors affecting the progress of development in Africa. The endogeneity problem is present in all of the three empirical papers examined. To circumvent this endogeneity problem and establish a credible causal effect, we explore the impact of Zambia’s 2002 Universal Free Primary Education (UFPE) policy which created an exogenous source of variation in education as a quasi – experiment. The three substantial empirical studies, employ the same econometric methodology, a Regression Discontinuity Design (RDD), whose appealing feature is local randomisation. This characteristic has distinguished the method from other evaluation methods in terms of estimating unbiased treatment effects. Another advantage of the fuzzy Regression Discontinuity design is that it can account for the endogeneity of the treatment variable. The utilisation of the fuzzy Regression Discontinuity design is a valuable contribution in all of the research. Furthermore, every chapter makes a unique contribution within its respective sector. We outline Zambia’s Universal Free Primary Education (UFPE) Policy and also present the Regression Discontinuity Design methodology framework. We find significant causal impacts of maternal education on child health measured by height-for-age, weight-for-height and Weight-for- age. The findings also indicate that maternal education is associated with a reduction in the prevalence of stunting and underweight and no effect wasting contrary to other research. We present evidence of the several mechanisms by which maternal education impacts child health. The results of our study indicate that a greater level of maternal education exerts a beneficial influence on child health through the postponement of marriage, the reduction in total fertility, and the delay in the age of first childbirth and sexual debut. Additionally, we have discovered indications of positive assortative mating. Furthermore, education empowers moms by facilitating their access to information via television and newspapers, equipping them with knowledge about the ovulation time, and helping them to make well-informed decisions regarding contraceptive techniques. Conventional wisdom posits that decreased fertility may indicate the presence of “superior quality” children and increased rates of survival for both mother and child. Can education serve as a catalyst for decreasing fertility rates in developing nations? We find that female education reduces iv | P a g e the number of children ever born. We present evidence of the reduction in total fertility as a result of female education. We also show that female schooling reduces the preferred number of children and increases the age at first birth. We find that female schooling affects fertility through age at first sex and marriage, literacy, assortative mating and the knowledge effect. There is no evidence to suggest that female schooling has a major impact labour market participation. We present evidence of the heterogeneous impacts of a mother’s education based on “poor versus wealthy” criterion, whether rural/urban status, region and religion. We also present evidence of the effect of female education on the HIV seroprevalence status, number of sexual partners and knowledge of HIV transmission mechanisms. We show that female education lowers HIV seroprevalence status, decreases the number of sexual partners and increases HIV knowledge. Our research suggests that educated women are more likely to have a deep and detailed understanding of HIV. Lastly, we present evidence of the heterogeneous effects of female education by household status on HIV related outcomes.Item Pharmaceutical patents and public health: facilitating access to affordable medicines in South Africa through trips flexibilities(University of the Witwatersrand, Johannesburg, 2024) Bouwer, Ryan; Andanda, PamelaThe Agreement on Trade-Related Aspects of Intellectual Property Rights (TRIPS) aims to strike a balance between the protection of creators and providing access to creative works to users of same. South Africa, as a member of the World Trade Organisation (WTO), has the flexibility to define its policy space in an internationally recognised and compliant manner to achieve an equilibrium between upholding public interest objectives and the private interests of patent holders in the field of health. South Africa has taken steps over the years to revise its medicine and intellectual property (IP) policies to address the issue of medicine access; however, implementation of reform is hampered by resource and capacity constraints, as well as economic and political pressures. As a result, the exorbitant pricing of pharmaceutical patented products continues to have an impact on the availability of essential medicines in South Africa. This report examines the functioning of the patents system in South Africa as it relates to the granting of pharmaceutical patents. The report discusses the link between intellectual property rights (IPRs) and public health and how the patent system can create barriers to access to affordable medicines. This report contends that the current patent climate exists due to shortcomings in South Africa’s Patent Act of 57 of 1978 (Patents Act) and its under-utilisation of TRIPS flexibilities. Pharmaceutical companies have exploited the current patent regime through evergreening and other abusive practises, resulting in the postponement of off-patent drugs and stifled competition, ultimately at the expense of public health. This report seeks to determine the extent to which South Africa has implemented TRIPS flexibilities in promoting access to affordable medicines in the realm of pharmaceutical patents, as well as whether South Africa can strike a balance between protecting pharmaceutical innovation and public health. It concludes by looking at how competition policy can be used to correct the imbalance and suggests that a focused and convergent approach to capacity building and transnational collaboration be employed.Item The constitutionality of COVID 19 Vaccination Policies and its implications on the right to freedom of religion in South Africa(University of the Witwatersrand, Johannesburg, 2024) Karuaihe, Janee Raahua SiegfriedCovid-19 was declared by the World Health Organisation (WHO) as a disease affecting people over a large geographical area. It caused severe illness to millions of people around the world and the death of over four million people. This impact on people had a direct effect on employers, employees and the workplace. Religions and those practicing their religion weren’t spared from the impact of Covid-19. To control the impact of Covid-19 on the workplace, employers were obligated to take steps to keep the workplace safe and to ensure that businesses can reopen in a manner that would ensure the safety of employees and the public. One of the measures taken by employers to ensure the safety of the workplace was the introduction of vaccination policies. These policies varied from workplace to workplace, but a consistent feature was that employees were required to be vaccinated to return to the workplace. If such workplace were to be implemented without exception, it would fail to recognise the fact that certain religious practices and certain people who practice various religions do not permit vaccines, and where they do, only certain vaccines are allowed. As there is no specific legislation governing the implementation of vaccination policies in the workplace, many employees across South Africa believed these policies unjustifiably limited rights protected by the Constitution, including the right to religion. The courts have accepted that vaccination policies may have the effect of limiting rights that are protected in terms of the Bill of Rights. Still, such limitations may be justified where the employer takes steps and introduces such a policy where necessary to ensure the safety of the workplace.Item In Silico Exploration of Endocannabinoid Receptor–CB1 and CB2–Interactions Comparing Cannabidiol and Cannabidiol Diacetate: A Comprehensive Computational Study(University of the Witwatersrand, Johannesburg, 2024-09) Soobben, Marushka; Achilonu, Ikechukwu Anthony; Sayed, YasienIn the rapidly evolving field of cannabinoid research, acetylated phytocannabinoids such as cannabidiol diacetate (CBDDA) have shown prominence due to its enhanced effects compared to its natural counterpart, cannabidiol (CBD). Despite the growing popularity in the consumption of acetylated phytocannabinoids, in-depth research on its pharmacological impact, especially on CB1 and CB2 receptors, remains scarce. With rising reports of adverse reactions to acetylated phytocannabinoids, a molecular understanding of their interaction with endocannabinoid receptors (CBRs) is imperative. This study aimed to fill this knowledge gap by analysing receptor interactions of CBDDA in comparison with receptor interactions of CBD. The study showed that CBDDA forms stronger interactions with CBRs than CBD. Recognised for its heightened potency, the potential of CBDDA as a biopharmaceutical product was examined. CBR interactions with known endocannabinoids, agonists and inverse agonists validated the computational models used to determine the difference in conformational dynamics upon ligand binding. In this work, bioinformatics, molecular docking, and molecular dynamics (MD) simulations were used to determine the structural differences of CBRs when bound to CBD/CBDDA. Simulations in a 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) and water environment successfully mimicked physiological conditions. Subsequent high-throughput virtual screening (HTVS) was conducted using CBDDA as a reference where ligands 142730975 and 21568811 were identified as the top scoring hits for CB1 and CB2 receptors, respectively. The identification of these ligands via HTVS highlights the therapeutic potential of targeting CBRs and the biopharmaceutical potential of CBDDA. This study elucidates the specific interactions of CBD and CBDDA with CB1 and CB2 receptors, laying a foundation for assessing the safety and efficacy of acetylated phytocannabinoids. Overall, the differential interaction of CBDDA compared to CBD with CBRs suggests that acetylation changes the conformational dynamics of CBRs thereby potentially affecting signalling. The identification of ligands 142730975 and 21568811 as strong interactors with the receptors may provide valuable leads for the development of new cannabinoid-based therapies.Item Realising the right to healthcare: the legislative frameworks pertaining to private health establishments and private healthcare funding models in South Africa(University of the Witwatersrand, Johannesburg, 2024) Labuschagne-Kom, Lindsie; Mahery, Prinslean; Martin, BlakeThe Universal Declaration of Human Rights recognises access to healthcare as a fundamental human right and is guaranteed by the South African Constitution. An analysis of this right reveals that it comprises of two main components, namely financing and delivery of healthcare services. These are fulfilled by the government in the public sector and by private healthcare funders and private health establishments in the private sector. However, an analysis reveals that access to healthcare is substantively inequitable due to the fragmentation of the health system and unveils significant inefficiencies in the private sector that impeded realisation of this right. This dissertation examines the cause of this fragmentation and the inefficiencies within the private healthcare funders and private health establishments market. It investigates how these issues can be resolved to realise the right to healthcare. This study applied a qualitative desktop review of governmental policies, direct and incidental legislation, and multidisciplinary fields of academic reviews such as competition, healthcare, constitutional law and international policies to evaluate the effect of historical, contemporary and prospective policies and legislation, on access to healthcare. This analysis reveals that access to healthcare was historically manipulated to achieve political ideology through a legislative framework that provided the foundation for private funding models and private health establishments to flourish. This occurred at the expense of the public sector and embedded the fragmentation and inefficiencies in the health system. Notwithstanding the enactment of the Constitution, which envisioned a transformed and equal society, access to healthcare remains substantively inequitable. This is due to governmental failings to regulate these stakeholders. Given this state of affairs, the government intends to enact legislative reform through the National Health Insurance Bill to meet its constitutional mandate to realise the right to healthcare. An analysis of the Bill’s framework, however, reveals that it will have a cascading effect with the collapse of the private healthcare funders and private health establishment markets. This will ultimately cause a regression in access to healthcare and impede the practical realisation of this right. An investigation into alternative mechanisms to fulfil the right to healthcare reveals that incorporation and collaboration with private healthcare funders and private health establishments is a pragmatic alternative to the National Health Insurance Bill that will aid with the practical realisation and vindication of this right. These findings indicate the need for government to improve its stewardship of the health system and provide pragmatic solutions to reform the legislative and regulatory frameworks governing these stakeholders to resolve inefficiencies and to foster collaboration to fulfil the right to healthcare.Item The price effects of a hospital merger: a case study of the Mediclinic Southern Africa (Pty) Limited (Mediclinic) and Matlosana Medical Health Services (Pty) Limited (MMHS) merger(University of the Witwatersrand, Johannesburg, 2024) Laurence, Marcelle; Mncube, LibertyThis study evaluates the assessment conducted in the prohibited Mediclinic Southern Africa (Pty) Ltd and Matlosana Medical Health Services (Pty) Ltd (MMHS) proposed merger. The study employs a qualitative approach, centred on a case study methodology, to assess the theories of harm discussed. It aims to provide insights into the adequacy and outcome of the competition authorities’ assessment drawing comparisons to international literature and policy implications. It uses economic theory to analyse and show the significance of robust and nuanced regulatory frameworks in healthcare merger evaluation.